A myocardial lead having a rigid helical coil adapted to be turned into heart tissue is disclosed by L. R. Bolduc in U.S. Pat. No. 3,737,579. The helical coil is a wire connected with an elongated flexible conductor to a pacemaker for transmitting electrical pacing currents to the heart. Interactions between the coil and the heart tissue can reduce the effects of the electrical stimulation. Fibrosis can occur around the coil which increases the chronic threshold and can result in trauma of the heart tissue to be stimulated. The configuration of the electrode can reduce mechanical trauma and minimize fibrosis. Thrombus formation can also be reduced by the administration of suitable drugs to the stimulation site. The delivery of a steroid drug to the stimulation site of an implantable pacing lead is disclosed by W. A. Berthelsen in U.S. Pat. No. 4,953,564. A controlled drug release device is integrated with the fixation helix such that as the helix is extended the controlled drug release device is concurrently extended. The controlled drug release device is limited to the immediate vicinity of the distal end of the helix to minimize the dispersion of the drug into the blood stream. The controlled drug release device has a porous elution path for accommodating the dispensing steroid.
A bi-polar cardiac electrode having a helical electrode and an annular electrode is disclosed by R. H. Rockland and D. H. Gobeli in U.S. Pat. No. 4,010,758. The annular electrode has a flat surface adapted for intimate contact with heart tissues so that a relatively intense electrical field is established through the heart tissue between the helical electrode and the annular electrode. A drug release device is not used with this bi-polar electrode.